Connected: An Internet Encyclopedia
RFC 1035 - 3.3.13. SOA RDATA format

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### 3.3.13. SOA RDATA format

        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        /                     MNAME                     /
        /                                               /
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        /                     RNAME                     /
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                    SERIAL                     |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                    REFRESH                    |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                     RETRY                     |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                    EXPIRE                     |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        |                    MINIMUM                    |
        |                                               |
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

where:

    MNAME           The <domain-name> of the name server that was the
                    original or primary source of data for this zone.

    RNAME           A <domain-name> which specifies the mailbox of the
                    person responsible for this zone.

    SERIAL          The unsigned 32 bit version number of the original copy
                    of the zone.  Zone transfers preserve this value.  This
                    value wraps and should be compared using sequence space
                    arithmetic.

    REFRESH         A 32 bit time interval before the zone should be
                    refreshed.

    RETRY           A 32 bit time interval that should elapse before a
                    failed refresh should be retried.

    EXPIRE          A 32 bit time value that specifies the upper limit on
                    the time interval that can elapse before the zone is no
                    longer authoritative.

    MINIMUM         The unsigned 32 bit minimum TTL field that should be
                    exported with any RR from this zone.

SOA records cause no additional section processing.

All times are in units of seconds.

Most of these fields are pertinent only for name server maintenance operations. However, MINIMUM is used in all query operations that retrieve RRs from a zone. Whenever a RR is sent in a response to a query, the TTL field is set to the maximum of the TTL field from the RR and the MINIMUM field in the appropriate SOA. Thus MINIMUM is a lower bound on the TTL field for all RRs in a zone. Note that this use of MINIMUM should occur when the RRs are copied into the response and not when the zone is loaded from a master file or via a zone transfer. The reason for this provison is to allow future dynamic update facilities to change the SOA RR with known semantics.

Next: 3.3.14. TXT RDATA format

Connected: An Internet Encyclopedia
RFC 1035 - 3.3.13. SOA RDATA format